In the related art, a projector which modulates light emitted from a light source according to image information and projects modulated light on a projection surface such as a screen is known. A projector (projection image display device) which is disposed close to the projection surface and includes a reflection optical system so as to make it possible to project an image by widening an angle is proposed (for example, see PTL 1).
The projection image display device described in PTL 1 includes an image light generating unit which generates image light and a projection optical system which projects image light emitted from the image light generating unit onto a projection surface. The projection optical system includes a refractive optical system and a reflection optical system reflecting image light emitted from the refractive optical system.
The refractive optical system includes a rear-stage casing provided at a side near the image light generating unit, a front-stage casing provided at a side far from the image light generating unit, a plurality of lens groups disposed in the rear-stage casing, and a plurality of lens groups disposed in the front-stage casing.
The front-stage casing includes a plurality of holding tools that respectively hold the plurality of lenses disposed inside thereof, a first mirror frame in which a straight groove is formed, and a second mirror frame in which a cam groove is formed. Each holding tool includes a guide pin and moves to the straight groove in such a way that the guide pin is disposed by being fitted into the straight groove and the cam groove and the second mirror frame is rotated. That is, the refractive optical system is configured in such a way that the second mirror frame is rotated and accordingly, lens held in each holding tool is moved along an optical axis of the refractive optical system and focus adjustment or the like is possible.
The reflection optical system includes a reflection mirror, for example, an aspherical mirror having a concave surface and reflects image light emitted from the refractive optical system.